Mobile cranes



United States Patent Frederick H. Tayler 201 Chartridge Lane, Chesham,England [2!] Appl. No. 767,350

[72} Inventor [22] Filed Oct. 14, I968 [45] Patented Dec. 15, 1970 [3 2]Priority May 3, 1968 [3 3 1 Great Britain [31 No. 20994/68 [54] MOBILECRANES 2,891,681 6/1959 Greivell 212/49 Primary Examiner-Harvey C.Hornsby Attorney-Shoemaker & Mattare ABSTRACT: A mobile crane providedwith a counterweight having a support member extending away from thecenter of gravity of the counterweight and including first and secondpivot points, with the first pivot point located further from the centerof gravity of the counterweight than the second, first and second linkmeans pivotally connected to a lower point and a higher point,respectively, on the crane and to the second pivot point and the firstpivot point, respectively, on the support member, and a hydraulic jackconnected to said links for controlling the angular positions of thelinks so that the counterweight is caused to be moved away from thecrane in such a manner that the line joining the first and second pivotpoints on the support member is rotated to increase the angle of theinclination of this line to the vertical.

MOBILE CRANES This invention relates to mobile cranes and isparticularly concerned with side-boom mobile cranes of the kind used forpipe laying. Such cranes may have a derricking jib at one side of thecrane and a counterweight on the other side of the crane to balance theload lifted by the crane. The axis of derricking movement of the .jib isnormally parallel to the longitudinal axis of the crane and thecounterweight may be arranged to be swung outwardly from the crane abouta further axis parallel to the longitudinal axis of the crane-The cranewill normally be a tractor-mounted, but may also be a tractordrawn,crane.

It is an object of the invention to provide a novel system of mountingthe counterweight on the crane in order to increase its effectiveness inbalancing the load lifted by the crane.

The term counterweight" is used'herein to describe not only the weightsthemselves, which may 'be, for example, blocks of metal or concrete, butalso any framework provided to carry these weights. Further, the termcrane" is used herein to include the vehicle on which the jib and otherparts of the crane proper are mounted.

The invention consists in a mobile crane provided with a counterweightmounted on first and second links pivotally connected to the crane andto the counterweight, and a hydraulic jack controlling the angularpositions of said links, wherein the pivot points are so located and thelinks are so dimensioned that, as the pivot points onthe counterweightare moved away from the crane by operation of the hydraulic jack, theline joining these pivot points is'rotated in such a direction as toincrease the distance between the centre of gravity of the counterweightand the crane.

It will normally be desirable to use two counterweights on a mobilecrane in accordance with the invention, and in the case of a side-boommobile crane, for example; the two counterweights will be mountedside-by-side with corresponding pivots coaxial and parallel to thefore-and-aft axis of the crane.

It will be seen from FIG. 2 that each of the links8is'in the form of asolid bar, whereas each of the links 14 is channelshaped in crosssection. The two links 14 are interconnected by means of a frameworkconsisting of two horizontalmembers 16 and 17 and two diagonal members18 and I9.

The positions of the counterweights are controlled by means of twohydraulic jacks, one of which is shown at 20. The cylinder of each jackis pivotally secured to the respective bracket 11 by means of anextension of the shaft which constitutes the pivot point for the link 8.The lower end of the piston rod of each of the hydraulic jacks ispivotally connected to an intermediate point 21 on the respective linkI4. The lefthand link 14 is shown broken away in FIG. 2 to show thebearing 22 and the shaft 23 constituting the pivotal connection for oneof the piston rods. When the pistons of the two hydraulic jacks aredrawn as far as possible into their respective cylinders, the weightsare fully retracted so that the links 14 are substantially vertical.Under these conditions each hydraulic jack 20 is located substantiallywithin the cross section of its associated link 14. One advantage ofthis arrangement is that each jack acts in a more direct line with itsassociated link and the excessive bending moments which occur on thecylinder anchorage points in some known systems are eliminated.

When hydraulic fluid is admitted to the cylinders to extend the twohydraulic jacks, the two pairs of links 8 and 14 will be rotatedclockwise as seen in FIG. 1, and the counterweights l and 2 will beswung outwardly from the tractor. It will be seen that thecounterweights will be not only displaced laterally but also rotatedabout the pivot points 5 and, when the jacks are fully extended, thelines joining the pairs of pivot points 4 and 5 will becomesubstantially horizontal. In this position the centre of gravity of eachcounterweight is displaced outwardly A separate hydraulic jack willnormally be provided with each counterweight but the two first linkswill be interconnected by means of a bracing framework.

One embodiment of the invention willnow be described with reference tothe accompanying diagrammatic drawings in which g FIG. 1 is a rear viewof a part of a side-boom mobile crane in accordance with the inventionhavingthe counterweights partially extended, and

FIG. 2 is a side view of the embodiment shown-in FIG. 1 with thecounterweight retracted. v

. In the arrangement illustrated in the drawings, the crane is providedwith two counterweights generally indicated by the reference numerals land 2. Each counterweight includes a support member 3 which extends awayfrom the centre of gravity of the respective counterweight and isprovided with a first pivot point 4 and a second pivot point 5, thepivot 4 being, in each case, located further from the centre of gravityof the respective counterweight than the pivot point 5. As can be seenfrom the left-hand side of FIG. 2 the pivot point 4 includes a bearing 6and a shaft 7 rotatable in this bearing. The shaft 7 is secured to alink 8 by means of a nut 9. The other end of the link 8 is pivotallyconnected to a pivot point 10 secured to the crane, for example, bymeans'of a bracket 11 fitted to a winch frame 12.

The pivot point 5 includes a bearing-l2 in which a shaft 13 isrotatable. The shaft 13 is secured to a link 14, the other end of whichis pivotally connected to the crane at 15. It will be seen that thepivot point I0 is almost directly vertically above the pivot point 15and that, when the counterweightis retracted, the two links 8 and 14 aresubstantially vertical, the pivot point 4 being above the pivot point 10and the pivot point 5 being above the pivot point 15. Furtherundertheseconditions, the centre of gravity of the counterweight l isbelow the two pivots points 4 and 5 and the support member 3 is soshaped that the centre of gravity of the counterweight is in-' board ofthe links 8 and 14.

from the crane but remains in substantially the same horizontal plane aswhen the counterweights were retracted. In the particular arrangementillustrated, when the counterweights are fully extended, the two pivotpoints '10, the two pivot points 4 and the two pivot points 5 are allcontained substantially in the same horizontal plane. Rotation of eachcounterweight causes its centre of gravity to be displaced not merely bythe length of the respective link 14 but also by the distance betweenthe pivot point 5 and the said centre of gravity.

The increased leverage produced by the linkage system illustratedenables a substantially lower weight of counterweight to be used than isnecessary in known balancing systems. Furthermore, the arrangementillustrated enables the centre of gravity of each counterweight, when itis retracted, to be lower and nearer to the centre line of the tractorthan in conventional counterweight systems.

Since a system in accordance with the invention enables thecounterweights to be extended further from the crane than in knownsystems the total weight required to balance a given load is lower thanin known systems. Hence, the overall weight distribution of the crane issubstantially improved in comparison with existing designs. Mobilecranes are usually employed under the most arduous conditions, andtherefore weight and applied ground pressure must be kept to a minimum.Furthermore, on a side-boom mobile crane, it is inevitable that themachine will be unbalanced when travelling light, and the lower theweight of the counterweights the better will be the weight distributionand overall balance of the crane. Similarly the better balance and loweroverall weight of a crane in accordance with the invention facilitatesthe transportation of the crane from site to site and it will normallyno longer be necessary for counterweights to be moved for transportationpurposes.

Iclaim:

l. A mobile crane provided with a counterweight including a supportmember extending away from the centre of gravity of the'counterweightand provided with first and second pivot to the second pivot point onthe support member; a second :1 link one end of which is pivotallyconnected to a higher pivot point on the crane and the other end ofwhich is pivotally consnected to the first pivot point on the supportmember; and, a ahydraulic jack connected to said links controlling theangular positions of said links in such a way that, as the counterweightis moved awaytfrom the crane by operation of the hydraulic jack, theline joining the first and second pivot points on the r'support memberis rotated in such a direction as to increase "the angle of inclinationof this line to the vertical.

" 2. A mobile crane as in claiml, wherein a pair of counterweights areprovided, each mounted on first and second links 'pivotally connected tothe crane and to the respective counterweight; a pair of hydraulicjacks, each extending between "the crane and a respective one of saidlinks; and a bracing framework interconnecting said two first links.

3. A crane as claimed in claim 1, wherein, when the counterweight isretracted, the two links are substantially vertical, the counterweightpivot point being in each case above the corresponding crane pivot pointand the two pivot points on the counterweight being locatedsubstantially vertically one above the other 7 4. The crane as claimedin claim 3, wherein the centre of

